1. Field of the Invention
The present invention relates to a vibrating transport apparatus capable of transporting a predetermined weight of articles placed on a trough for a given length of time by vibrating the trough.
2. Description of the Prior Art
It has been often experienced that when a food material such as, for example, snacks and/or candies is produced, articles in the form of granulates or the like of a raw material or a semi-processed products is transported by the use of a vibrating transport apparatus (hereinafter referred to as a vibrating feeder) from one production step to another at a predetermined supply rate, that is, in a predetermined weight for a given unitary time. The vibrating feeder of the type used in this application makes use of a weighing device utilizing a load cell for measuring the entire vibrating feeder, while the articles supplied from a supply conveyor onto the trough are transported, at intervals of a short unitary time, so that the weight of the articles on the trough of the vibrating feeder can be measured by subtracting the known weight of the vibrating feeder from the measured total weight. Based on the weight of the articles so measured, a transport amount control device of the vibrating feeder controls the transport speed of the supply conveyor on a PID (Proportional Integral Differential) control scheme so that the weight of the articles supplied from the supply conveyor onto the trough can attain a predetermined value for the given unitary time. At this time, in order to compensate for an error based on a delay in the PID control, a correction control to finely adjust the transport speed of the vibrating feeder is carried out to render the amount of the articles being transported (weight/time) towards the subsequent production step to attain a value equal to the target transport amount.
Where the articles such as snacks and/or candies are to be bagged, the articles are fragmented in a predetermined quantity by a combinational weighing apparatus utilizing the load cell referred to above.
A mechanism of the combinational weighing apparatus is schematically shown in a side view in FIG. 18. The articles M are supplied through a supply chute 60 onto a center portion of a conical dispensing feeder 61 having a small height. When the dispensing feeder 61 is vibrated, the articles M are dispensed into a plurality of vibrating feeders 1 arranged around and adjacent the periphery of the dispensing feeder 61 and spaced an equal distance from each other in a direction circumferentially of the dispensing feeder 61. The articles M on the vibrating feeders 1 are subsequently transported towards a corresponding number of pool hoppers 62 disposed immediately below the associated vibrating feeders 1. After the articles M are temporarily pooled in the respective pool hoppers 62 in synchronism with a weighing operation, discharge gates of the pool hoppers 62 are opened to allow the articles M to be discharged onto associated weighing hoppers 64. A weighing means 65 such as a load cell for each weighing hopper 64 measures the weight W of the articles M within the respective weighing hopper 64 to provide a weight signal. The articles M of which the weight W has been measured are, when discharge gates 66 of the weighing hoppers 64 are opened, collected in corresponding collecting chutes 67 and then onto a discharge chute 68. The articles M so discharged are bagged by a bagging machine (not shown) to provide bagged products each having a predetermined target weight. Each of the weighing hoppers 64 has preset therein a target weight to which the articles M are supplied and, therefore, depending on the extent of the weighed value relative to the target value, the respective amplitudes or the respective vibrating time lengths of the vibrating feeders 1 are adjusted so that the weighed value can become equal to the target value.
With the conventional combinational weighing apparatus, the weight detection or the control of the amount of transport of the articles on each of the vibrating feeders 1 is carried out by reading the weight measured by the associated weighing hopper 64, that is, the weight measured at a location downstream of the respective vibrating feeder 1 and not by reading accurately on a real-time basis the weight or the amount of transport of the articles on the respective vibrating feeder 1. Therefore, a considerable time lag tends to be involved along with an insufficient response. For this reason, it has been found difficult to accomplish an accurate control of the amount of the articles to be supplied (that is, the transport amount).
Also, in the prior art vibrating feeder 1 of the type discussed above, since a load cell is used to measure the total weight of the vibrating feeder 1 having a relatively great weight, the apparatus as a whole tends to become bulky and expensive.
In addition, in the prior art vibrating feeder 1, the control of the transport amount, that is, the amount of the articles to be transported by the vibrating feeder 1 is carried out by changing driving energies (electric driving power) to change the amplitude of vibration of the vibrating feeder 1. Accordingly, if the transport amount is increased by increasing the amplitude of vibration of the vibrating feeder 1, the amount of heat evolved by an electromagnetic coil tends to increase, accompanied by increase of energies consumed.
Yet, when the vibrating feeder is to be halted, the articles tends to be transported under the influence of an inertia even though the driving energies are interrupted, and therefore, an error in transport amount tends to become considerable.
Accordingly, the present invention has been devised with a view to substantially eliminating the above discussed problems inherent in the prior art and is intended to provide an improved vibrating transport apparatus capable of accomplishing the detection of the weight of the articles or the transport amount control accurately on a real-time basis with minimized energy consumption and also having a high response exhibited when the apparatus is brought to a halt.
Another important object of the present invention is to provide an improved vibrating transport apparatus of the type referred to above, which has a simplified structure enough to allow the vibrating transport apparatus to be assembled compact in size, and which is capable of accomplishing a highly accurate measurement of the weight of the articles on the trough and also capable of highly accurately controlling the rate of supply of the articles towards the subsequent production step with a simplified control system.
A further important object of the present invention is to provide a method of detecting a vibrating characteristic exhibited in the vibrating transport apparatus of the type referred to above.
In order to accomplish these objects, the present invention according to a first aspect thereof provides a vibrating transport apparatus for transporting an article loaded on a trough by vibrating the trough in a predetermined vibrating direction, which apparatus comprises a weight detector including at least one strain gauge mounted on a portion of the transport apparatus where elastic strains are developed upon placement of the article on the trough and operable to detect an amount of the strains, and a weight detecting circuit for detecting a weight of the article placed on the trough on the basis of the amount of the strains detected by the strain gauge.
According to the present invention, since the amount of the strains detected by the strain gauge changes with change in weight of the article on the trough, the weight of the article on the trough can advantageously be detected on a real-time basis. Also, no extra weight detector is needed in the vibrating transport apparatus.
In one preferred embodiment of the present invention, the vibrating transport apparatus may further comprise an amplitude detector including an additional strain gauge mounted on a portion where elastic strains are developed as a result of vibration of the trough and operable to detect an amount of the strains, and an amplitude detecting circuit for detecting an amplitude of vibration of the trough on the basis of the amount of the strains detected by the additional strain gauge. This additional strain gauge may be employed in common with the strain gauge of the weight detector.
According to this feature, since the amplitude of vibration of the trough can be detected from the amount of strains detected by the additional strain gauge, no extra amplitude detector is needed in the vibrating transport apparatus.
In another preferred embodiment of the present invention, the strain gauge of the weight detector or the amplitude detector may be mounted on a portion of a spring member for elastically supporting the trough therethrough on a base.
In a further preferred embodiment of the present invention, the strain gauge of the weight detector is mounted on a portion of an elastic member for elastically supporting the base therethrough on a machine framework. The elastic member may be in the form of a rubber block, a coil spring or a vibration damper.
According to this structure, in addition to the capability of detecting the weight of the article on the trough, a bias of the article on the trough can also be detected.
The present invention according to a second aspect thereof provides a vibrating transport apparatus which comprises a weight detector for detecting a weight of the article placed on the trough; a storage means for storing an amplitude versus weight characteristic of a vibrating system of the trough; and a transport control means for determining an amplitude corresponding to the weight of the article, which has been detected by the weight detector, from the storage means, calculating a transport amount for a given unitary time from the determined amplitude and the weight of the article, and controlling the transport apparatus on the basis of the transport amount which has been calculated.
According to this feature, the weight of the article is detected by the weight detector as placed on the trough, not at a location downstream of the transport apparatus with respect to the direction of transport of the article, and the transport amount of the article can be calculated on a real-time basis from the detected weight and the amplitude of vibration of the trough obtained from the storage means in correspondence with the detected weight. By controlling the vibrating frequency, the amplitude of vibration and the operating time of the transport apparatus on the basis of the calculated transport amount, the transport apparatus can be accurately controlled.
In a further preferred embodiment of the present invention, the weight detector may include at least one strain gauge mounted on a portion of the transport apparatus where elastic strains are developed upon placement of the article on the trough. This feature makes it possible to assembly the weight detector in a simplified structure and compact in size.
The present invention according to a third aspect thereof provides a vibrating transport apparatus which comprises a weight detector for detecting a weight of the articles placed on the trough; an amplitude detector for detecting an amplitude of vibration of the trough; and a transport control means for calculating a transport amount for a given unitary time from the weight of the article, which has been detected by the weight detector, and the amplitude which has been detected by the amplitude detector and controlling the transport apparatus on the basis of the calculated transport amount.
According to this feature, the transport amount of the article can be calculated on a real-time basis with the use of the weight of the article on the trough detected by the weight detector and the amplitude of vibration of the trough detected by the amplitude detector. By controlling the vibrating frequency, the amplitude of vibration and the operating time of the transport apparatus on the basis of the calculated transport amount, the transport apparatus can be controlled accurately.
The present invention according to a fourth aspect thereof provides a vibrating transport apparatus which comprises at least one strain gauge mounted on a spring member used to connect the trough and a base together; a weight detecting circuit for detecting a weight of the article placed on the trough on the basis of an electric output from the strain gauge; an amplitude detecting circuit for detecting an amplitude of vibration of the trough on the basis of the electric output from the strain gauge; and a transport control means for calculating a transport amount for a given unitary time on the basis of the detected weight and the detected amplitude and controlling the transport apparatus on the basis of the calculated transport amount.
According to this feature, the transport amount of the article can be calculated on a real-time basis with the use of the weight of the article on the trough and the amplitude of vibration of the trough, both detected from the amount of strains detected by the strain gauge mounted on the spring member. By controlling the vibrating frequency, the amplitude of vibration and the operating time of the transport apparatus, the transport apparatus can be controlled accurately.
The present invention according to a fifth aspect thereof provides a vibrating transport apparatus which comprises an amplitude detector for detecting an amplitude of vibration of the trough; a storage means for storing an amplitude versus weight characteristic of a vibrating system of the trough; and a transport control means for determining a weight of the article placed on the trough on the basis of the amplitude, which has been detected by the amplitude detector, and the amplitude versus weight characteristic stored in the storage means, calculating a transport amount for a given unitary time on the basis of the determined weight of the article and the detected amplitude and controlling the transport apparatus on the basis of the calculated transport amount.
According to this feature, the transport amount of the article can be calculated on a real-time basis with the use of the amplitude of vibration of the trough detected by the amplitude detector and the weight of the article obtained from the storage means. By controlling the vibrating frequency, the amplitude of vibration and the operating time of the transport apparatus, the transport apparatus can be controlled accurately.
The present invention according to a sixth aspect thereof provides a vibrating transport apparatus which comprises an amplitude detector for detecting an amplitude of vibration of the trough; a storage means for storing a resonance frequency characteristic of a vibrating system of the trough which corresponds to a weight of the article placed on the trough; and a transport control means for determining a weight of the article placed on the trough on the basis of the amplitude, which has been detected by the amplitude detector, and the resonance frequency characteristic stored in the storage means, calculating a transport amount for a given unitary time on the basis of the determined weight of the article and the detected amplitude and controlling the transport apparatus on the basis of the calculated transport amount.
According to this feature, the transport amount of the article can be calculated on a real-time basis with the use of the amplitude of vibration of the trough detected by the amplitude detector and the weight of the article obtained from the storage means. Moreover, since the weight of the article is determined by the utilization of the resonance frequency characteristic stored in the storage means in correspondence with the weight of the article, the accurate weight can be obtained and, hence, the calculated transport amount becomes accurate. Accordingly, by controlling the vibrating frequency, the amplitude of vibration and the operating time of the transport apparatus, the transport apparatus can be controlled more accurately.
The present invention according to a seventh aspect thereof provides a vibrating transport apparatus of a type designed to transport an article loaded on a trough by vibrating the trough in a predetermined vibrating direction with a vibrator. This transport apparatus comprises a frequency adjuster for adjusting a driving frequency of the vibrator; and a frequency control means for controlling an amplitude of vibration of the trough by controlling the frequency adjuster to change the driving frequency of the vibrator.
According to this feature, since the amplitude of vibration is changed with change of the driving frequency, the driving energies can be effectively utilized by using the driving frequency to approach a resonance point at all times.
The present invention according to an eighth aspect thereof provides a vibrating transport apparatus which comprises a frequency adjuster for adjusting a driving frequency of the vibrator; and a frequency control means for braking a transport of the article by controlling the frequency adjuster to change the driving frequency of the vibrator in a direction required to attenuate an amplitude of vibration of the trough.
According to this feature, by interrupting the supply of the driving energies after the amplitude of vibration of the trough has been abruptly attenuated by changing the driving frequency, a braking can be applied in a high response.
The present invention according to a ninth aspect thereof provides a vibrating transport apparatus which comprises a frequency adjuster for adjusting a driving frequency of the vibrator; a storage means for storing a resonance frequency characteristic of a vibrating system of the trough; and a frequency control means for controlling an amplitude of vibration of the trough by controlling the frequency adjuster on the basis of the resonance frequency characteristic, stored in the storage means, to change the driving frequency of the vibrator.
According to this feature, not only can the driving energies of the vibrator be utilized effectively, the amplitude of vibration can be shifted accurately to that effective to change the amplitude of vibration of the trough by changing to the driving frequency corresponding to the amplitude of vibration desired to be adjusted on the basis of the resonance frequency characteristic stored in the data storage means.
The present invention according to a tenth aspect thereof provides a vibrating transport apparatus which comprises a frequency adjuster for adjusting a driving frequency of the vibrator; a weight detecting means for detecting a weight of the article placed on the trough; a storage means for storing a plurality of amplitude versus driving frequency characteristics of a vibrating system of the trough which correspond to the weight of the article on the trough; and a frequency control means for controlling an amplitude of vibration of the trough by controlling the frequency adjuster on the basis of the amplitude versus driving frequency characteristic, corresponding to the weight of the article detected by the weight detecting means, to change the driving frequency of the vibrator.
According to this feature, the weight of the article is detected by the weight detector as placed on the trough, not at a location downstream of the transport apparatus with respect to the direction of transport of the article, and the driving frequency is changed to correspond to the amplitude of vibration desired to be adjusted on the basis of the amplitude versus driving frequency characteristic stored in the storage means in correspondence with the detected weight. Accordingly, the amplitude of vibration of the trough can quickly be changed to the amplitude desired to be changed, accompanied by increase in response. Also, since the driving frequency of the vibrator is changed, the driving energies can be utilized effectively.
The present invention according to an eleventh aspect thereof provides a vibrating transport apparatus which comprises a frequency adjuster for adjusting a driving frequency of the vibrator; and an amplitude detector for detecting an amplitude of vibration of the trough; a storage means for storing a relation between the amplitude, detected by the amplitude detector when the driving frequency of the vibrator is changed, and the driving frequency; and a frequency control means for controlling the amplitude of vibration of the trough by controlling the frequency adjuster on the basis of the amplitude versus driving frequency characteristic, stored in the storage means, to change the driving frequency of the vibrator.
According to this feature, by changing the driving frequency to a value corresponding to the amplitude of vibration desired to be adjusted on the basis of the amplitude versus driving frequency characteristic stored in the storage means, the amplitude of vibration of the trough can quickly be changed to a desired value accurately. Also, since the driving frequency of the vibrator is changed, the driving energies can be utilized effectively. In addition, since it is possible to store the amplitude versus driving frequency characteristic, which is determined during operation of the transport apparatus by the use of the amplitude detector, in the storage means, it is possible to pursue for change in characteristic of the apparatus with high sensitivity.
The present invention according to a twelfth aspect thereof provides a vibrating transport apparatus which comprises a frequency adjuster for adjusting a driving frequency of the vibrator; an amplitude detector for detecting an amplitude of vibration of the trough; a weight detector for detecting a weight of the article placed on the trough; a storage means for storing a relation between the amplitude, detected by the amplitude detector when the driving frequency of the vibrator is changed under the detected weight of the article, and the driving frequency in correspondence with the weight of the article; and a frequency control means for controlling the amplitude of vibration of the trough by controlling the frequency adjuster on the basis of the amplitude versus driving frequency characteristic, stored in the storage means in correspondence with the detected weight of the article, to change the driving frequency of the vibrator.
While the amplitude versus driving frequency characteristic changes with change of the weight of the article, the foregoing feature makes it possible to store in the storage means the amplitude versus driving frequency characteristic corresponding to the detected weight of the article and also to change the driving frequency to a value corresponding to the amplitude of vibration desired to be adjusted on the basis of contents stores in the storage means. Therefore, the amplitude of vibration of the trough can be more accurately shifted to the amplitude desired to be changed. Also, since the driving frequency of the vibrator is changed, the driving energies can be utilized effectively. Furthermore, since it is possible to store in the storage means the amplitude versus driving frequency characteristic of the transport apparatus that is determined by the amplitude detector during operation of the transport apparatus, it is possible to pursue for change in characteristic of the apparatus with high sensitivity.
The present invention according to a thirteenth aspect thereof provides a vibrating transport apparatus which comprises a trough for receiving an article thereon; a base; at least one leaf spring for supporting the trough therethrough on the base; a vibrator for vibrating the leaf spring; a weight detector for detecting a weight of the article placed on the trough; an amplitude detector for detecting an amplitude of vibration of the leaf spring; a data generating means for generating a data representative of a relation between a driving frequency of the vibrator and the amplitude detected by the amplitude detector by utilization of the weight of the article, detected by the weight detector during transport of the article by means of the trough, as a parameter; and a storage means for storing the data generated by the data generating means.
According to this feature, the data generating means automatically generates a data representative of the relation between the driving frequency of the vibrator and the amplitude detected by the amplitude detector by utilization of the weight of the article, detected by the weight detector during transport of the article by means of the trough, as a parameter, which data are stores successively in the storage means. Thereafter, when the transport amount is to be calculated, the weight of the article is obtained from the weight detector and the amplitude data of the trough corresponding to the driving frequency of the vibrator are read out from the storage means to cause the calculating means to precisely calculate the transport amount of the article on a real-time basis.
In one preferred embodiment, the weight detector may comprise at least one strain gauge mounted on the leaf spring for detecting an amount of strains developed in the leaf spring, and a weight detecting circuit for detecting the weight of the article on the basis of the amount of strains detected by the strain gauge. With this structure, since the weight of the article on the trough can be detected from the amount of the strains detected by the strain gauge mounted on the leaf spring, no extra weight detector is needed in the transport apparatus.
Also, in a preferred embodiment of the present invention, the amplitude detector may comprise at least one strain gauge mounted on the leaf spring for detecting an amount of strains developed in the leaf spring, and an amplitude detecting circuit for detecting the amplitude on the basis of the amount of strains detected by the strain gauge. This makes it possible to dispense with any extra amplitude detector since the weight of the article on the trough and the amplitude of vibration of the trough can be detected from the amount of strains detected by the strain gauge mounted on the leaf spring.
The present invention furthermore provides a method of detecting a vibrating characteristic of a vibrating transport apparatus. This method comprises the steps of transporting an article by vibrating a leaf spring, supporting therethrough on a base a trough on which the article is placed, with a vibrator, detecting a weight of the article on the trough and an amplitude of vibration of the leaf spring, and generating a data representative of a relation between a frequency of vibration of the trough and the detected amplitude with the weight taken as a parameter. With this method, the data representative of the relation between the vibrating frequency of the vibrator and the amplitude of vibration of the leaf spring detected by the amplitude detector can be automatically generated during operation of the vibrating transport apparatus, the data so generated being successively stored in the storage means.